Chord Formulas: Cm9, Major, Minor, and Suspended Chord-naming Rules

The chord Cm9 (C minor 9th) is comprised of these notes:

C E♭ G B♭ D

In this case, the chord is called a “minor 9th” because the underlying chord is a minor chord (actually a minor 7th chord, Cm7).

Chord formulas come from the application of a few basic rules. If the name of the chord has the word ...

“minor” in it, such as “C minor 7th” (Cm7) or “C minor 9th” (Cm9), then it’s a minor triad, usually with an added flatted 7th (and more notes may be added)
“major” in it, such as “C major 7th” (CMaj7) or “C major 9th” (CMaj9), then it’s a major triad, usually with an added natural 7th (and more notes may be added)
“suspended” in it, such as “C suspended 4th” (Csus4) or “C suspended 2nd” (Csus2), then it’s a triad in which the note in scale position 3 has been removed and replaced with the note in scale position 4, or 2 (e. g., instead of C, E, G, you’d have the notes C, F, G or C, D, G, respectively)